Ansys-cfx simulations – multiple size group (musig) model for bubble coalescence and break-up in multiphase flows

The main focus of the CFD department at HZDR is the qualification of CFD-codes for multiphase flows. This includes particularly model development as well as validation and testing based on high quality experimental data obtained at the TOPFLOW experimental test facility operated especially for this purpose in the research center. The models developed at HZDR are implemented into the commercial CFD-code CFX produced by the ANSYS Inc. Corporation.
The talk discusses the development of the MUSIG (Multiple-Size-Group) model for poly-disperse turbulent gas–liquid mixtures and its extension to phase change. It includes the development of a generalized model for bubble coalescence and breakup in turbulent bubbly flow, which takes into account all important mechnisms. The generalization makes it possible to use a unified set of models for different flow configurations and avoid arbitrary adjustment. The validation results for adiabatic air-water and evaporating/condesning steam-water flows are presented. In addition, the implementation of appropriate heterogeneous nucleation models for boiling flow is discussed.